1. Field of the Invention
The present invention belongs to a technical field of a circuit board, film carrier, etc. for mounting a semiconductor device.
The present application is based on Japanese Patent Application No. Hei. 10-263712, which is incorporated herein by reference.
2. Description of the Related Art
Various types of circuit boards have been proposed each for mounting a bare chip (which is obtained by individually cutting out a collection of a large number of integrated circuits repeated formed on a wafer) of the integrated circuit.
FIG. 4 shows an example thereof in which a bare chip 30 is mounted on a circuit board 20 and resin-sealed. In this example, a plastic substrate (polyimide substrate) 21 is used in place of a lead frame. The plastic substrate 21 is connected to an electrode pad used on an active face of the bare chip 30 (upper face of the bare chip in the drawing) through a gold wire 50 by wire bonding.
However, the circuit board as shown in FIG. 4 suffers from basic problems (contact between the wires and upper limit of a wire loop) of wire bonding due to high density wiring of electrode pads or arrangement of an area pad on the bare chip. In order to connect the wire to the active face of the bare chip, the deactive face (lower face in the drawing) is secured to the substrate. Therefore, the heat of the device cannot be effectively diffused from the non-active face. In addition, an increase in the wiring length in the wire bonding limits a transmission characteristic of a high speed signal. Further, as seen from FIG. 4, an adhesive layer 40 for fixing the bare chip 30 to the circuit board 20 must be prepared separately.
FIG. 5 shows another example of a circuit board for mounting the bare chip in which a bare chip 30 is mounted on a circuit board 20 and resin-sealed like FIG. 4. The example shown in FIG. 5, in which the circuit board 20 is connected to the bare chip 30 through a beam lead, also suffers from the problem of high density and area pad arrangement. In addition, an adhesive buffer material (elastomer) 41 must be separately prepared between the circuit board 20 and the bare chip 30.
In order to solve the above problems, a circuit board as shown in FIG. 6 has been proposed in e.g. Japanese Patent 202506 xe2x80x9cWIRING BOARD AND ITS MANUFACTURING METHODxe2x80x9d, Japanese Unexamined Patent Publications Nos. Hei. 2-229445, 2-229442, 3-046262 and 3-062533. As seen from FIG. 6, the circuit board 20 for mounting an element or device is provided with bump contacts 22. The bump contacts 22 are directly connected to the electrode pads formed on the active face of the bare chip 30 to solve the above problem of high density and area pad arrangement. Further, the mounting face of the substrate is given adhesive property so that the adhesive layer and buffer agent must be prepared separately.
In the circuit board as shown in FIG. 6, it is recommended to use an excimer laser for hole processing for a conductive path for forming a bump or hole processing on the back face of the circuit board. However, the excimer laser requires complicate management, takes high running cost and cannot realize mass-production.
An object of the present invention is to solve the above problem to provide a substrate for mounting a semiconductor element having a structure which can be manufactured at low cost and high mass-productivity, and its manufacturing method and use.
(A) The substrate for mounting a semiconductor device is characterized by comprising: an insulating substrate; a first circuit pattern formed on the first main surface of said insulating substrate; an insulating layer covering the circuit pattern, the insulating layer being made of a photosensitive and thermally-melting type adhesive resin; a contact formed on the surface of the insulating layer, the contact being connected to the circuit pattern by a first conductive path passing through the insulating layer; a conductive layer formed on the second main surface of the insulating substrate opposite to the first main surface; and the conductive layer and the insulating substrate having a through-hole into which the circuit pattern is exposed.
(B) The semiconductor device according to the present invention is one in which a semiconductor element is mounted on the mounting substrate according to the present invention is characterized in that the contact of the substrate is connected to an electrode pad of the semiconductor device, and the insulting layer is bonded onto a surface of the semiconductor element on the side of the electrode pad by heating.
(C) The method of manufacturing a substrate for mounting a semiconductor element is characterized by comprising the steps:
(a) preparing a member of an insulating substrate on the first main surface of which the first circuit pattern is formed and on the second main surface of which a conductive layer is formed having an opening into which the insulating substrate is exposed at a position corresponding to the first circuit pattern;
(b) forming an insulating layer covering the circuit pattern formed in the step of (a) using an insulating material of a photosensitive and thermally-melting type adhesive resin;
(c) forming a through-hole in the insulating layer formed in step (b) through exposure/development processing, thereby exposing the first circuit pattern into the through-hole;
(d) filling the through-hole with conductor formed in step
(c), thereby forming a first conductive path passing through the insulating layer to provide a contact on the surface of the insulating layer; and
(e) removing the insulating substrate exposed into the opening of the conductive layer using the conductive layer in step (a) as a mask so that the opening is passed through the conductive layer and the insulating substrate and the first circuit pattern is exposed into the opening.
Hereinafter, the substrate for mounting a semiconductor element is also referred to xe2x80x9cmounting substratexe2x80x9d.
By using, as a material of the insulating layer on which a semiconductor element is mounted, an insulating material which is a photosensitive and thermally-melting type adhesive resin, only the presence of this insulating layer simultaneously satisfies the following two points:
(1) In order to form a conductive path for a contact point on the insulating layer, hole processing can be performed through exposure/development using photosensitivity. This permits the excimer laser to be omitted.
(2) In mounting of the semiconductor device, the surface of the insulating layer is bonded to the active face of the element. This removes necessity of preparing an adhesive layer between the element and the mounting substrate.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.